A magnetic recording medium of a so-called magnetic metal thin film type, in which a magnetic material of metal or an alloy such as Co--Ni is directly deposited by plating or a vacuum thin film forming technique (e.g. vacuum deposition, sputtering or 1on plating) on a base film, such as a polyester film or a polyimide film, has a number of advantages, that is, it is superior in coercivity, rectangular ratio or in electromagnetic transducing characteristics for a short wavelength range, while the magnetic layer can be reduced in thickness for reducing demagnetization due to recording or thickness losses during playback. In addition, the packing density of the magnetic material may be increased because there is no necessity of mixing a non-magnetic binder into the magnetic layer.
In the magnetic metal thin film type recording medium, the magnetic layer is generally formed by vacuum deposition. For example, the magnetic layer is deposited by a so-called continuous take-up type oblique evaporation method in which an evaporated magnetic material is deposited on the base film which is caused to run in a vacuum chamber from a supply side to a take-up side so as to travel on the outer peripheral surface of a cooling can provided on the travel path of the base film.
Meanwhile, when the magnetic metal thin film type magnetic recording medium is employed in, above all, a digital video tape recorder, since the data transfer rate is extremely high, the relative velocity between the magnetic recording medium and the magnetic head during recording and playback needs to be at least twice the recording velocity for conventional analog recording. Since a considerable damage is done in this manner to the magnetic recording medium, it has become crucial to improve durability of the magnetic recording medium.
However, if oxygen be introduced during vacuum deposition for providing a protective layer, such as a Co oxide, on the surface of the magnetic layer, sufficient durability of the magnetic recording medium cannot be achieved. For this reason, it becomes additionally necessary to provide a protective film of an abrasion-resistant material. Besides, if simply the protective film is increased in thickness, there is a risk that electro-magnetic transducing characteristics be deteriorated due to spacing losses.
In view of the above-described status of the art, at is an object of the present invention to provide a magnetic recording medium which is improved in abrasion resistance without incurring deterioration of the electromagnetic transducing characteristics and which is superior in durability and reliability, and a method for producing such magnetic recording medium.